Ever since we first heard about Pixar's upcoming film Inside Out at the 2011 D23 Expo, we've been so excited to hear more about this intriguing new film. Recently, Pete Docter revealed some new information about working on the animated film, which will take place inside the mind of an 11-year-old girl.

In an interview with the Hollywood Reporter at the CG convention Siggraph, Inside Out director Pete Docter referred to the upcoming project as “one of the most challenging stories I’ve ever had to put together.” The film will feature two stories: what's going on in the girl's life, and what's going on inside her head, with emotions such as anger, sadness, disgust, and joy becoming main characters in the action. About the challenges that come along with this, Docter said:

“One story is hard enough. This is two stories that need to talk to each other.”

However, Docter seems to remain optimistic about the challenging project, which he says “takes advantage of what animation can do.” About the film's animation, Docter commented:

“The characters are created with this energy because we are trying to represent what emotions would look like. They are made up of particles that actually move. Instead of being skin and solid, it is a massive collection of energy.”